Plant pathogens have a profound impact on agricultural production. Accordingly, the control and eradication of certain plant viruses is of economic importance. One plant pathogen of economic interest is the potato virus Y. That virus is a member of the polyviridae family, the largest known group of plant viruses. Potato virus Y infects and causes damages in several plant species, including members of the Solanaceae family. In one member of that family, comprising species of potato, infection by potato virus Y may result in as high as an 80% reduction in crop yield. However, despite its name, potato virus Y is pathogenic in a variety of plant species, including non-potato species.
Of interest to the present invention is the P1 gene of potato virus Y. That gene encodes one of eight functional proteins produced by processing of a primary polyprotein encoded by the 9.7 Kb genome of potato virus Y. Protein P1 is encoded near the 5' end of the viral genome and is a 35 kDa protein having C-terminal proteolytic activity. The P1 protein has also been reported to bind RNA. Brantley, et al., J. Gen. Virol., 74:1157-1162 (1993).
Also of interest to the present invention are reports that genetically-engineered pathogen-derived resistance to viral pathogens has been achieved in several plant species. For example, resistance to viral infection has been reported in plants transformed with viral coat protein-encoding genes. Hull, et al., Grit. Rev. Plant Sci., 11: 17-33 (1992). Recently, there have been several reports that resistance to a plant virus may be achieved by transforming a susceptible plant with non-structural genes of the virus. However, such attempts have produced relatively strain-specific resistance. For example, strain-specific viral resistance has been reported by transformation of a strain of tobacco with replicase genes of tobacco mosaic virus. Longstaff, et al., EMBO J., 12:379-386 (1993). Similar strain-specific result in tobacco have been reported by transformation with potato virus Y. Audy, et al., 12 Annual Meeting of the American Society of Virology, University of California at Davis, Calif. 7 (1993). Finally, strain-specific resistance to potato virus Y infection has been reported in tobacco having been transformed with the NIa proteinase of potato virus Y.
To date, methods for introduction of viral resistance in plants, and especially methods for achieving resistance to potato virus Y and other economically-important viruses, have been relatively strain-specific. Moreover, there are no reports of the use of P1 to generate resistance to any virus in potatoes or any other species. Accordingly, there is a need in the art for a method for conferring resistance to viral pathogen across a range of species. In addition, due to the economic importance of controlling plant pathogens, and especially plant pathogens infecting food crops, there is a need in the art for additional transgenic virus-resistant species and methods for making such transgenic species.